What about folders that represent tags? I could tag a file (say a picture) with Danny (my name), Vacation, and 2007. The system creates 4 "folders" as we understand them, each one labeled with a tag, and the final one labeled as "images" or something similar (whatever the file type is). You could open the "images" folder and see the image, along with all other images. You could drill down further into images>vacation and see all files tagged with both images and vacation. You will also see additional folders for other items that have additional tags and fit in the images>vacation tag.
You could also get to the same file by going into the "Danny" folder, to see all files tagged with "Danny,"
It's a little difficult to explain, and I'm sure that what I'm trying to express is already being developed by someone, but either way, it is a more efficient system than what we already have. No more annoying shortcuts and restrictive folders.